The importance of typography in aircraft piloting systems

We're surrounded by screens these days
-- we sit at desks at work, carry phones in our pockets, use GPS in
the car, and soon we'll look straight through screens in the
corners of our vision as we're conducting our daily business. We
might appreciate the form factor of a new device, or coo at the
pinpoint sharpness of a display, or the convenience of the
placement of a particular button. But what makes these devices
usable, and easy to decipher and integrate into our field of
vision? Visual design.

Typography, and the screen technology it is presented on, has a
very powerful influence on how we absorb, retain, and process
information. By extension, this means that someone with control
over an aircraft, carrying several hundred people in an aluminium
tube whose 5mm thick skin protects the soft flesh of those inside
from a minus 70 degree, 0.85 Mach airflow, needs to be able to very
easily read their instruments. Again, and again, and again. All
night, in the dark, all year long. Physiology and anatomy dictate
that certain design considerations be taken into account when
creating iconography for aircraft displays -- delicate, colour
symbols on high quality, non flickering displays are not always the
obvious choice they might appear.

One experienced pilot with more than 5000 hours airtime
as a 747-400 pilot states that in a dark cockpit, in haste, it has
been known for the wrong fuel shut-off to be
switched

Airlines, like most commercial concerns, depend on being able to
leverage maximum usage from their assets in a given timeframe (a
basic fit Airbus A380 costs around $300 million). This includes
aircraft, personnel, and the systems that keep the two working
smoothly together. Fatigue has been cited in a number
of aircraft accidents. While instrumentation and flight display
technology cannot be blamed or factored into every incident where
crew fatigue is suspected, it is logical that the more challenges
there are to the pilot's ability to maintain a constant and
accurate "scan" of their instruments, the more likely they are to
experience increased fatigue as a result of this process.

To that end, aircraft displays have now largely come to resemble
a row of laptop screens, rather than the seemingly endless series
of dials and switches featured in older aircraft (many of which
remain in service today). The information presented on those
displays is carefully filtered to show pilots what they need, when
they need to see it, with the aim of minimising the odds of
important information being misunderstood, or just plain missed.
For example, the 747-400 fuel system diagram in the image below
allows a pilot to very quickly assess visually whether fuel is
flowing between a given fuel tank and the aircraft's engines. A
text-based cue may, in stress, lead to the wrong fuel system being
disconnected and potentially lead to the wrong engine being shut
down. One experienced pilot with more than 5000 hours
airtime as a 747-400 pilot states that "in a dark cockpit, in
haste, it has been known for the wrong
fuel shut-off to be switched. Hence history has shown there is
greater danger from prompt, incorrect action, than waiting 20
seconds with a burning engine until the other crew member has spare
capacity to check you, before you pull the switch."

The 747-400 fuel system diagram in the image below allows a pilot to very quickly assess visually whether fuel is flowing between a given fuel tank and the aircraft's engines

Indeed, when driving, government guidelines suggest drivers should glance at displays
for no more than 1.5 seconds -- when travelling at 60 miles per
hour, that equates to a distance of 40 metres with the driver's
eyes off the road. When you place these recommendations into an
aviation context, you can multiply the speeds and distances
travelled by around a factor of 10 for most commercial aircraft. In
congested airspace, at night, and in bad weather, the challenge for
crews to absorb essential information swiftly and accurately is a
significant one.

Similarly, EICAS displays on the 747-400 allow crew members to
very quickly assess the performance of their four engines using a
"milk bottle" analogy. The milk bottles fill from the bottom as
thrust is increased, with white indicating normal operation, amber
indicating that performance is in the "cautionary" range, and red
when a limit is exceeded.

EICAS displays on the 747-400 allow crew members to very quickly assess the performance of their four engines using a "milk bottle" analogy

Compare this to the Hercules C130K's engine state panel (on the
right) -- a visually complex array of dials, needles, and extremely
small figures. While experience and training coupled with practised
crew cooperation undoubtedly allow the effective use of a system
like this, it's hard to argue that the EICAS system is harder to
read. It's reasonable to expect high contrast LCD displays and
easily readable text have an impact on the safe operation of the
aircraft -- especially in a four engine aircraft, with four times
as many sets of performance data being presented to the pilot.

In their
paper, 'Legible, are you sure?', which looks at the
implications of typographical design in aircraft systems, Jean-Luc
Vinot and Sylvie Athènes from the University of Toulouse, state
that "the large number of available digital fonts, as well as the
published guidelines should not lead us to consider that legibility
is no longer an issue of concern. On the contrary, a special effort
should be made to prove the safety, usability and performance of
this software component. The creation of a numeric typeface
necessarily involves highly specialised knowledge in the field of
design and typography. The critical area of use of these fonts also
requires the contribution of particularly rigorous evaluation
methodologies of the kind used by experimental sciences."

Despite this, their preliminary analysis of proposed systems
found that "text density can be quite overwhelming. Character
design itself has some flaws that tend to bring about confusion
between some letters. Significant problems were found concerning
visual spacing, letter size or contrast. Lastly, fonts used on
different views are sometimes heterogeneous. The close proximity or
overlapping of graphical elements (highlights, framing, weather
information, maps) can significantly interfere with legibility". In
other words, despite multifunction displays reducing the pilot's
requirement to look at lots of dials, many challenges still exist
in ensuring that what is presented is done so with great care.

Another major concern is terrain avoidance. Fear of flying's
great irony is that the further away from the ground you are, the
safer you tend to be for longer. Garmin Aviation's recent
developments in terrain display during night flight are a major breakthrough
in civil aviation safety and, if linked to a radar altimeter and
autopilot, might even provide a very similar experience to the RAF's venerable
Tornado GR4 and its terrain-following radar capability. Imagine
it: the dead of night, 480 knots, in the Cairngorms, and
it's raining. You take your hands off the stick and throttle and
sit back while the aircraft maintains a set height and ride
smoothness from every obstacle in your path. It's a leap of faith,
but perhaps no greater than that which we take every time we board
a flight as passengers.

The difference for us passengers is that the Tornado GR4 crew
are limited to a narrow, toilet tube style view through their night vision goggles as
the hillsides flash past between the clouds, plus the view from
their FLIR (forward looking infrared) sensor. Civilian pilots, and
those flying upcoming jets like the F35 Lightning 2, can now be
treated to a widescreen, high contrast panel view with a graphical
representation of the terrain ahead rendered into their field of
view. This enhancement in situational awareness, coupled with the
kind of visual cues that good icon design and carefully chosen typefaces provide, is a
boon to air crew, and we'll be seeing it in cars as a standard
feature within the next few years. Imagine seeing glowing outlines
of people crossing the road 500m in front of you in thick fog, or a
flashing red symbol overlaid on an object lying in the road.

Airbus has leveraged what it's learnt in earlier generations of aircraft and made the A380's cockpit, displays, and ergonomics so similar to its predecessors that pilots can cross-qualify on different aircraft types and easily switch from one to another without costly retraining, all aided by the best display technology, type and symbology design

The enormous A380 even has dedicated displays for airfield
plates -- detailed maps of the taxiways, gate numbers, and other
essential details to allow safe ground navigation around ever
larger airports. Airbus has leveraged what it's learnt in earlier
generations of aircraft and made the new jet's cockpit, displays,
and ergonomics so similar to its predecessors that pilots can
cross-qualify on different aircraft types and easily switch from
one to another without costly retraining, all aided by the best
display technology, type and symbology design.